fix: fix when compiling with 2.12

Author: He-Pin

actor/src/main/scala/org/apache/pekko/dispatch/VirtualThreadSupportReflect.scala

@@ -55,7 +55,8 @@ private[dispatch] object VirtualThreadSupportReflect {
       }
       val nameMethod = ofVirtualClass.getDeclaredMethod("name", classOf[String], classOf[Long])
       val factoryMethod = builderClass.getDeclaredMethod("factory")
-      builder = nameMethod.invoke(builder, prefix + "-virtual-thread-", 0L)
+      val zero = java.lang.Long.valueOf(0L)
+      builder = nameMethod.invoke(builder, prefix + "-virtual-thread-", zero)
       factoryMethod.invoke(builder).asInstanceOf[ThreadFactory]
     } catch {
       case NonFatal(e) =>